Accelerator or choke? (8)
I believe the answer is:
throttle
I believe this is a double definition.
'accelerator' is the first definition.
('throttle' can be a synonym of 'accelerator')
'choke' is the second definition.
('throttle' can be a synonym of 'choke')
'or' is the link.
(Other definitions for throttle that I've seen before include "Fuel-regulating valve in an engine" , "Accelerator - choke" , "Strangle; control (an engine)" , "Strangle with car part" , "Strangle; fuel controller" .)